The electroslag remelting process essentially comprises the fusing from a consumable electrode of metal to be refined under a blanket of molten slag. The molten slag is introduced into the mold and acts as an electrical conductor for the electrical current passing between the consumable electrode and the base plate of the mold. The current heats the molten slag, and in turn, the electrode and drops of the metal fuse off of its lower end and fall to the bottom of the mold where a pool of molten metal forms and solidifies upwardly. A refining action takes place in the molten metal drops as they pass through the molten slag. As the electrode is progressively consumed, the refined metal builds up from the bottom of the mold with the molten slag floating on the pool of refined metal and being maintained in contact with the lower end of the consumable electrode. The refining process through the slag continues until the electrode is consumed or substantially consumed.
Special slags are generally used in the electroslag refining process. Although they have a high dielectric constant in the solid form, they are conductive to some extent in the liquid phase. Moreover, in the molten state, slag with a significant portion of calcium fluoride is highly liquid and has a corrosive effect on ordinary refractory. In view of this characteristic, furnaces for melting such slag prior to introducing same into the electroslag mold often comprise specially formed graphite. However, such graphite furnaces are frequently expensive and their construction may add substantially to the cost of the electroslag refining process. On the other hand, furnaces which include bricks composed of other than graphite often have to be replaced which necessarily takes the furnace out of the production and, unless a replacement is provided, may hold up production for uncertain periods with resulting additional costs and inefficiency. A need thus exists for a slag melting furnace for the electroslag refining process which is reasonable in cost, effective and efficient in operation and which can be utilized for comparative extended periods without the requirement for undue repairs or rebricking.